Declarations

procedure GammaBlur32(ASource, ADest: TBitmap32; Radius: TFloat); overload;
procedure GammaBlur32(Bitmap: TBitmap32; Radius: TFloat); overload;
procedure GammaBlur32(Bitmap: TBitmap32; Radius: TFloat; const Bounds: TRect); overload;
procedure GammaBlur32(Bitmap: TBitmap32; Radius: TFloat; const Region: TArrayOfFloatPoint); overload;

Overload Details

Overload 1

procedure GammaBlur32(ASource, ADest: TBitmap32; Radius: TFloat); overload;

Blurs the source bitmap in linear light space and writes the result into the destination bitmap.

Parameter	Type	Description
ASource	TBitmap32	Source 32-bit bitmap to read pixels from.
ADest	TBitmap32	Destination 32-bit bitmap to receive the blurred output.
Radius	TFloat	Blur radius in pixels.

Overload 2

procedure GammaBlur32(Bitmap: TBitmap32; Radius: TFloat); overload;

Blurs the entire bitmap in-place using linear light space.

Parameter	Type	Description
Bitmap	TBitmap32	Bitmap to blur in-place.
Radius	TFloat	Blur radius in pixels.

Overload 3

procedure GammaBlur32(Bitmap: TBitmap32; Radius: TFloat; const Bounds: TRect); overload;

Blurs a rectangular sub-region of a bitmap in-place using linear light space.

Parameter	Type	Description
Bitmap	TBitmap32	Bitmap containing the sub-region to blur.
Radius	TFloat	Blur radius in pixels.
Bounds	TRect	Bounding rectangle defining the target sub-region.

Overload 4

procedure GammaBlur32(Bitmap: TBitmap32; Radius: TFloat; const Region: TArrayOfFloatPoint); overload;

Blurs an arbitrary polygonal region of a bitmap in-place using linear light space.

Parameter	Type	Description
Bitmap	TBitmap32	Bitmap containing the polygonal region to blur.
Radius	TFloat	Blur radius in pixels.
Region	TArrayOfFloatPoint	Array of 2D floating-point points defining the polygon vertices.

Description

GammaBlur32 performs gamma-aware Gaussian blurring on 32-bit ARGB bitmaps.

Unlike Blur32, which operates directly on non-linear sRGB pixel values, GammaBlur32 converts pixel channels into linear light space before applying the recursive filter passes, and converts the result back to sRGB space afterwards.

Why Use Gamma-Aware Blurring?

Standard blurring on non-linear sRGB pixels underestimates physical photon luminance along transitions between bright highlights and dark shadows. This results in noticeable dark fringe artifacts (a dark halo along white-on-black text or antialiased shapes).

By performing channel filtering in linear light space, GammaBlur32 ensures physically accurate light blending and clean, natural edge falloffs.

Example

var
  Bmp: TBitmap32;
begin
  Bmp := TBitmap32.Create;
  try
    Bmp.LoadFromFile('high_contrast_text.png');

    // Perform gamma-correct Gaussian blur to avoid dark edge halos
    GammaBlur32(Bmp, 8.0);

    Bmp.SaveToFile('gamma_blurred.png');
  finally
    Bmp.Free;
  end;
end;

See also

• Blur32
• HorizontalBlur32
• GR32_Gamma
• GaussianRadiusToSigma